Research On Property Of Train Flow In City Express Railway System Based On Cellular Automata

The complex traffic flow of urban railway traffic was studied with the cellular automata theory. The basic characteristics of railway traffic flow under the specific circumstances when two kinds of trains with different capacities were operating in the same metro line, and when a certain train was broken down, stopped between two stations, and later be rescued were analyzed. More emphasis was placed on run-stop wave and trains'delay transfer. The potential benefits of adjusting the operation interval and dwell time on alleviating trains'delay were also simulated and analyzed with the proposed model.Based on real traffic system and the basic principles of moving block system, two cellular automaton models were proposed to simulate the subway railway traffic where different trains with different performances were running in the same track, and to simulate the situation of subway when train accident occurred and rescue plan was performed. The main contents and obtained results are as follows:1. A cellular automaton model was proposed for urban railway traffic system. With this model the influence of train length, acceleration, and maximum speed on traffic flow was studied. More work was focused on the trains' delay caused by the differences of trains'performances. Simulation results showed that:differences in trains'length would disturb the traffic flow, and delay the following trains; differences in acceleration had insignificant influences on the property of train flow; differences in maximum speed would probably result in trains'longtime delay, and many trains were running late in this case.2. Another cellular automata model was proposed to simulate the railway traffic flow when a certain train broke down and delayed the following trains. In this model, the characteristic behaviors of railway traffic from the time when a train broke down and stopped till it was rescued and pushed to the stop line in the next station were reproduced. Trains'delay transfer caused by the rescuing process was reproduced and scrutinized. The time-speed and time-space trajectories of the faulty train and rescuer train were also analyzed. The simulation results proved that the proposed model was able to simulate the occurrence of train failure and reproduce the complex behaviors of train movements in railway transit system.3. Based on the foregoing model, another model more close to the situations in practical subway system was proposed. In this model, the railway traffic flow when accidents occurred in different sections was reproduced. The simulation results revealed that if the location of accident was far away from the stop line, more time would be spent in rescuing the faulty train and pushing it to the stop line, and thus more trains would be delayed. These results are in accord with the theoretical situation, thus can provide advices for designing the location of stop lines in subways.